Gas phase olefin polymerization with single site catalysts has been a well-established art field since the invention of metallocene catalysts over two decades ago. Although, single site polymerization catalysts (such as metallocene catalysts, constrained geometry catalysts, and phosphinimine catalysts) are often chosen for their very high activity, the use of such catalysts can lead to reactor fouling especially in a fluidized bed gas phase reactor. Such fouling may include polymer agglomeration, sheeting, or chunking, and may ultimately require reactor shut down.
In order to improve reactor operability, several specialized catalyst preparative methods, operating conditions, and additives have been used to modify the performance of metallocenes and to reduce reactor fouling.
European Patent Application No. 630,910 discusses reversibly reducing the activity of a metallocene catalyst using a Lewis base compound such as for example an amine compound.
Long chain substituted alkanolamine compounds in particular, have been used in combination with metallocenes to reduce the amount of reactor fouling in fluidized bed polymerization processes. The use of substituted alkanolamines in combination with metallocene catalysts to improve reactor operability and reduce static levels is described in European Pat. Appl. No. 811,638 and in U.S. Pat. Nos. 5,712,352; 6,201,076; 6,476,165; 6,180,729; 6,977,283; 6,114,479; 6,140,432; 6,124,230; 6,117,955; 5,763,543; and 6,180,736. Alkanolamines have been added to a metallocene catalyst prior to addition to a reaction zone, as described in U.S. Pat. Nos. 6,140,432; 6,124,230 and 6,114,479. Alkanolamines have also been added directly to a reactor or other associated parts of a fluidized bed reactor processes such as the recycle stream loop as is taught in European Pat. Appl. No. 811,638 and in U.S. Pat. No. 6,180,729, respectively.
There has been no systematic exploration of the effect of long chain substituted amines, including monoalkanolamines and dialkanolamines, on supported phosphinimine catalysts.